Irradiation of paraffin wax



United States Patent 3,014,854 IRRADIATION 0F PARAFFIN WAX William W. Elliott, Lincolnwood, and Hallard C. Meyer,

Homewood, llh, assignors to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Filed Ian. 15, 1957, Ser. No. 634,150

3 Claims. ((11. 204- 162) This invention relates to petroleum wax having anti- 7 static properties and to a method for the preparation thereof.

which has been manufactured using such a wax.

This invention also relates to waxed paper Electrical non-conductance is a property which is typical of waxes in general and petroleum waxes in particular. While this property is desirable in specific instances, e.g., where wax is used as an insulating medium, in other instances it is detrimental because it permits buildup of electrostatic charges on wax films or on articles coated with a wax film.

This electrostatic buildup is particularly pronounced where wax is used to coat a non-conducting material such as paper, plastic, or wood, and it may result in such undesirable effects as attraction for dirt and lint, or a tendency to cling to other surfaces with which it comes in contact. For example, when paper is waxed on high speed waxing equipment or when waxed paper is handled on high speed packaging equipment, the paper may build up large electrostatic charges. Subsequently, this charged paper tends to adhere to itself or other surfaces, making it difficult to handle. A web of paper acquires electrostatic charges during waxing which it retains as the paper is collected on a rewind roll, creating a strong attractive force between adjacent layers in the finished roll of paper. This attraction may be strong enough to hamper unwinding the roll at a later date, and may even be strong enough to disrupt the wax film, harming its appearance and usefulness.

The hazard of sparks caused by static electricity is well known. Sparks from electrostatic discharges during high speed paper waxing operations constitute such a hazard.

Heretofore, attempts have been made to reduce the tendency of waxes to acquire and retain electrostatic charges by adding an anti-static agent to the wax. Such agents as soaps, glycols, sulfonates, salts, and graphite have met with very limited success because of poor compatibility and adverse elfects on wax appearance and performance.

It has been observed that the tendency to acquire an electrostatic charge during waxing is particularly pronounced in the case of petroleum wax prepared from a specific fraction of a Mid-Continent type petroleum. The fraction of petroleum in question is known as heavy lube distillate, and it consists of that fraction having an initial boiling point at 0.1 mm. of mercury absolute pressure of approximately 365 F. (generally from 340 F.

to 390 F.) and an end point at 0.1 mm. of mercury absolute pressure of approximately 500 F. (generally from 475 F.'to 525 F.). The petroleum wax is obtained from the heavy lube distillate by any conventional dewaxing operation, such as by precipitation of a slack wax from a methyl ethyl ketone-toluene mixture at low temperature. The slack wax may contain up to about 30 percent by weight of occluded oil, and this oil is removed by recrystallizing the wax one or more times from additional amounts of solvent (solvent deoiling) to provide a wax having less than about one percent by weight of oil, and preferably less than about 0.5 percent by weight of oil. The resulting wax generally has a melting point in the range of about 145-155 F. (ASTM D87-42).

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In accordance with the present invention, it has been discovered that the tendency of this Wax to contribute to the buildup of high electrostatic charges during waxing operations is markedly reduced by exposing the wax to high-energy radiation, particularly gamma radiation (radiation having a wave length of approximately 10- to 10- centimeters). A radiation dosage of approximately 2.0 l0 roentgens is eifective and higher dosages of the order of x 10 are even more effective. The wax as such can be subjected to the high-energy radiation, or it can be subjected to the radiation after it has already been applied to a different non-conducting material, such as paper, plastic or wood. The improvement obtained by subjecting the wax is not transient, and it does not appear to be afifected by melting or remelting the wax or by aging the irradiated wax before or after coating.

Surprisingly, the improvement in anti-static properties is obtained only with the wax described above. For example, a fully refined parafiin wax of 136 F. melting point prepared by a method similar to that described above, except that it was derived from a lower boiling lube distillate (boiling range 250 F. to 426 F. at an absolute pressure of 0.1 mm. of mercury) did not show a significant change in anti-static properties after irradiation dosages of as much as 188x10 roentgens. It is surmised that this difierence in anti-static properties is related to dissimilan'ties in structure, the wax from the heavy lube distillate having, for example, a lower percentage of normal paraffins and a higher percentage of branched and cyclic structures.

The following example illustrates various embodiments falling within the scope of this invention.

Example temperature and the radiation was applied at the rate of approximately 1 10 roentgens per hour. Also, two pound samples of a 136 F. melting point wax prepared from lube distillate having an initial boiling point at an absolute pressure of 0.1 mm. of mercury of 250 F. and a final boiling point at the same pressure of 425 F. were subjected to the gamma radiation in the amounts of 313x10 180x10 370x10 and 138.0 10 roentgens.

Two inch by eight inch strips of 26 pounds per ream (3000 sq. ft.) bleached sulfite were waxed in the conventional manner with the surface coating of 1012 pounds per ream on one side and 0.1-0.5 pound per ream on the back side, employing irradiated samples of the waxes prepared as described and also employing samples of the waxes which had not been subjected to gamma radiation.

Each strip was placed on a paper pad (for support) and given five quick, light strokes with a glass rod. Each strip was then removed from the pad and laid on a bed of cellophane discs contained in a flat glass dish. The cellophane discs were A inch diameter punchings from a one mil sheet. The strips were then lifted from the glass dish and the number of adhering discs counted.

The following results were obtained on the two waxes described.

1. A method for the production of wax having antistatic properties which comprises subjecting paraffin wax having a melting point in the range of about 145 to 155 F. prepared from heavy petroleum lube distillate having an initial boiling point of approximately 365 F. at an absolute pressure of 0.1 mm. of mercury and a final boiling point of approximately 500 F. at an absolute pressure of 0.1 mm. of mercury derived from Mid-Continent petroleum to radiation consisting of gamma rays in an amount within the range of about 2.0 10 to 100x10 roentgens and sufficient to substantially increase the anti-static properties of the Wax.

2. Wax having anti-static properties prepared by the method of claim 1.

3. Paper which has been waxed with wax prepared by the method of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,138,868 Liberthson Dec. 6, 1938 2,350,330 Remy June 6, 1944 2,904,482 Thwaites et a1 Sept. 15, 1959 OTHER REFERENCES Progress Report on Fission Products Utilization VIII, May 1956, BNL 389(T-73), pp. 17 and 18.

Chemical Age (January 8, 1955), page 153. 

1. A METHOD FOR THE PRODUCTION OF WAX HAVING ANTISTATIC PROPERTIES WHICH COMPRISES SUBJECTING PARAFFIN WAX HAVING A MELTING POINT IN THE RANGE OF ABOUT 145 TO 155*F. PREPARED FROM HEAVY PETROLEUM LUBE DISTILLATE HAVING AN INITIAL BOILING POINT OF APPROXIMATELY 365* F. AT AN ABSOLUTE PRESSURE OF 0.1 MM. OF MERCURY AND A FINAL BOILING POINT OF APPROXIMATELY 500*F. AT AN ABSOLUTE PRESSURE OF 0.1 MM. OF MERCURY DERIVED FROM MID-CONTINENT PETROLEUM TO RADIATION CONSISTING OF GAMMA RAYS IN AN AMOUNT WITHIN THE RANGE OF ABOUT 2.0X10**6 TO 100X10**6 ROENTGENS AND SUFFICIENT TO SUBSTANTIALLY INCREASE THE ANTI-STATIC PROPERTIES OF THE WAX. 